This research was planned to establish a functional assay for a single protein molecule. To recognize individual protein molecules, electron microscopy, which is the most prominent in the spacial resolving power, was employed. As the biological function recognizable with electron microscopy, we have chosen the iron-incorporation process conducted by ferritin molecules, which could store iron of up to 3500 atoms, easily identified with the mirosocpy, For the two-years research duration, following new findings were obtained.1)A single molecular functional assay of iron-incorporatibility of ferritin is established with TEM and high resolution SEM2)Ferritin molecules stably adsorbed onto silicon surface shows about 20% residual function on iron-incorporability compared with those in the solution phase3)Low on high pH condition drastically impairs the iron-incorporation activity of ferritin molecules when stably adsorbed onto silicon surface4)Anti-correction between the functional stability and the strength of adsorption is observed5)Ferritin molecules transfered from the mercury surface to the carbon surface in keeping the array form can maintain the iron-incorporability up to 85%.6)The closely packed array form of ferritin molecules are very stable in maintaing activity compared with those sparsely and randomly adsorbed on carbon surface.